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Meaning of Last Letter of UK National Insurance Number

Updated on July 31, 2016
Beth Eaglescliffe profile image

Beth is an entrepreneur. She writes about employment issues, ways to earn money and how to get best value when spending it.

Every British Worker has a National Insurance Number

Oxy-fuel cutting the grate that previously supported wisteria
Oxy-fuel cutting the grate that previously supported wisteria | Source

NI Number is a Stand-in for UK Identity Card

The United Kingdom has no formal identity card or document. In most cases a person’s passport is the document used to prove their identity. As recently as 2010, there was an attempt by the UK government to introduce compulsory ID cards, but the idea was very unpopular. The government eventually dropped the scheme because of protests about such documents becoming an unnecessary invasion of privacy.

However most people living in Britain are already on a national database without realising it. Once you are aged over sixteen years and start paid work in the United Kingdom you are automatically issued with a National Insurance (NI) number. A person’s NI number is very important as it is used to link employment records with social security benefits and tax payment records.

National Insurance Payments

National Insurance is paid by everyone working in the UK who earns over a certain amount. (For tax year 2015 -16, the threshold is £156 per week.) These contributions are recorded centrally and they determine eligibility for health and social security benefits including the State Pension.

Non-UK Passport Holders and National Insurance

Non-UK passport holders will not be issued with a National Insurance number unless they are resident in the UK for study or work purposes and hold an appropriate study or work visa. It is not possible to get a UK National Insurance number if you are only on vacation in the UK.

How to Apply For Your NI Number

Meaning of Your Unique NI Number and Letter Combination

Your National Insurance number may look like a random string of numbers and letters. Each person is issued with a unique number and letter combination. This number is individual to you and remains the same whether you move house or get married. The number is your personal identifier and remains the same throughout your life.

An NI (National Insurance) number consists of three parts. The first two letters are known as the prefix letters. These are followed by six numerals. Finally, there is a single suffix letter at the end of the string.

Prefix Letters

When the system first started, the two prefix letters were intended to represent the geographical location of the individual holding that National Insurance identity. However, the system was flawed because some areas of the country were more populous than others. Thus the number of unique combinations using the same two prefix letters was used up more quickly in some areas. So the system was changed.

The NI prefix letters that are currently used are not randomly generated. There is no publicly available information on how these new number combinations are generated. The UK government has decided to use the provisions of the Freedom of information Act 2000 to withhold the precise reasons for their choice.

Middle Random Number Sequence

The six numbers contained within each unique National Insurance number are a random sequence of numerals. These numbers are used by government departments like HMRC (Her Majesty’s Revenue and Customs) and the DWP (Department of Work and Pensions) as a unique identifier for each person.

Randomly Generated Sequences

Common House Martin flying in Czech Republic
Common House Martin flying in Czech Republic | Source

Suffix Letter

The lone suffix letter is a leftover identifier which relates to the manual collection of national insurance payments. Pre electronic record-keeping, a physical record of National Insurance payments was kept. Every employer had to literally buy a physical stamp and stick it onto a National Insurance card. There was one of these NI cards kept for each employee. The stamp proved that an employer had paid the appropriate NI contribution for that particular employee for that week.

There were millions of these cards and they needed to be checked annually by the government. In order for the checking to be spread evenly over each twelve month period, every NI card was linked to a particular month. This was signified by the suffix letter at the end of the National Insurance number. This ensured that during each three-month period, only one quarter of the nation’s National Insurance cards were being processed by the relevant government department.

For example, a card which had a suffix letter "A" would be sent for checking at the beginning of March.

The letter "B" was the designation for cards to be examined at the beginning of June.

The letter "C" showed that the card should be ready for inspection at the start of September.

The suffix "D" was for the final quarter of the year and was for cards to be checked in December each year.

With electronic processing and instant transfer of payments, the suffix letter of the U.K.’s National Insurance number has become irrelevant. However, it is still necessary to use it, as without the full unique combination, your National Insurance number will not be accepted as valid.

Unique British NI Number

Fictitious example
Prefix letters
originally linked to location
Middle numbers
random sequence
Suffix letter
shows season for audit

How to Get a UK National Insurance Number

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